Background In Belgium, a value set for children and adolescents for a generic health-related quality-of-life measure is not available. To inform drug pricing and make resource allocation decisions for children and adolescents, national tax-payers’ preferences for youth health states should be known. Objective We aimed to obtain a value set for EQ-5D-Y-3L in Belgium, following the international youth valuation protocol for data collection. Methods Composite Time Trade-Off interviews were conducted in a sample of 200 adults, either face to face or via video conferencing. Another sample of 1000 adults completed an online discrete choice experiment survey. All adults were asked to take the perspective of a 10-year-old child for both methods. Both samples were representative for Belgium in terms of age, sex and region. A latent class analysis was selected to obtain the relative importance of the five dimensions and their levels based on the discrete choice experiment data, which were anchored with the composite Time Trade-Off censored value for the worst health state (33333). Results Preferences from Belgian adults revealed a mean censored value for 33333 for children and adolescents of − 0.475. All the estimated coefficients of the model with 4 latent classes were statistically significant and showed higher disutility as severity levels increase. The most important health dimension was pain/discomfort, followed by feeling sad/worried/unhappy. Conclusions This study presents the Belgian EQ-5D-Y-3L value set, which will be included in the Belgian pharmacoeconomic guidelines. The value set enables the calculation of quality-adjusted life-years in children and adolescents, allowing a cost-effectiveness evaluation of health technologies and their youth-specific price setting. Supplementary Information The online version contains supplementary material available at 10.1007/s40273-022-01187-x.

Introduction/Aims Myasthenia gravis (MG) is a neuromuscular disease characterized by abnormal skeletal muscle fatiguability. The MG Activities of Daily Living (MG‐ADL) scale assesses eight symptoms and is often used as primary endpoint in MG clinical trials where it is completed by neurologists. However, in observational studies, patients frequently complete the MG‐ADL scale independently of their neurologist. In this study we aimed to assess the concordance between self‐ and physician‐reported MG‐ADL scores. Methods An international observational study was conducted among adult patients with MG scheduled for a routine visit or who entered the hospital via emergency services. Consenting patients and physicians completed the MG‐ADL. Concordance between assessments was calculated using Gwet's agreement coefficient (Gwet's AC) for the MG‐ADL individual items and the intraclass correlation coefficient (ICC) for the MG‐ADL total score. Results Data were collected from 137 patients (63% female; mean age, 57.7 years). Physicians assessed the patient's symptoms as slightly more severe (8.1 vs 7.5 MG‐ADL total score, respectively), corresponding to a difference of 0.6 on a range from 0 to 24. The ICC for the MG‐ADL total score between the patient and the physician assessment was 0.94 (95% confidence interval, 0.89 to 0.95), showing excellent concordance. Gwet's AC showed substantial to almost perfect agreement for all items, except eyelid droop, for which the agreement was moderate. Discussion Our results demonstrate that patients and neurologists have a concordant assessment of the patient's MG symptoms when using the MG‐ADL scale. This evidence supports patient self‐administration of the MG‐ADL in clinical practice and research.